Phosphor, light-emitting device, illumination device, image display device, and indicator lamp for vehicle

ABSTRACT

A phosphor having a favorable emission peak wavelength, narrow full width at half maximum, and/or high emission intensity is provided. Additionally, a light-emitting device, an illumination device, an image display device, and/or an indicator lamp for a vehicle having favorable color rendering, color reproducibility and/or favorable conversion efficiency are provided. The present invention relates to a phosphor including a crystal phase having a composition represented by a specific formula, and having a minimum reflectance of 20% or more in a specific wavelength region, in which the specific wavelength region is from the emission peak wavelength of the phosphor to 800 nm, and a light-emitting device comprising the phosphor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/JP2022/031466, filed on Aug. 19, 2022, and claims the benefit ofpriority to Japanese Application No. 2022-007317, filed on Jan. 20,2022, and to Japanese Application No. 2022-007319, filed on Jan. 20,2022. The content of each of these applications is hereby incorporatedby reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a phosphor, a light-emitting device, anillumination device, an image display device, and an indicator lamp fora vehicle.

Description of the Related Art

In recent years, there has been a turn toward energy-saving, and demandfor illumination and back lighting using LEDs is increasing. The LEDsused in these cases are white light-emitting LEDs in which a phosphor isarranged on an LED chip that emits light in a blue or near ultravioletwavelength.

An LED using, on a blue LED chip, a nitride phosphor that emits redlight and a phosphor that emits green light, with blue light from theblue LED chip as excitation light, has been used for this type of whitelight-emitting LED in recent years. Greater emission efficiency for LEDsis sought, and a phosphor having superior light emission characteristicseven as a red phosphor and a light-emitting device comprising such aphosphor are desired.

As a red phosphor that is used in a light-emitting device, a KSFphosphor represented by the general formulas K₂(Si, Ti)F6:Mn andK₂Si_(1-x)Na_(x)AkF₆:Mn (0 < x < 1), an S/CASN phosphor represented bythe general formula (Sr, Ca)AlSiN_(3:)Eu, and the like are knownexamples, but the KSF phosphor is harmful as a Mn-activated compound andso a phosphor that is better for humans and the environment is sought.In addition, many S/CASN phosphors have comparatively broad full widthsat half maximum (in other words, FWHM or spectral half peak width) ofabout 80 nm-90 nm and an emission wavelength band is likely to include awavelength range with low relative luminous efficiency, and therefore interms of improving conversion efficiency, a red phosphor with a narrowerfull width at half maximum is sought.

In addition, a phosphor represented by the composition formulaSrLiAl₃N₄:Eu is disclosed in an embodiment in Patent Literature 1, forexample, as a red phosphor that can be applied to recent light-emittingdevices.

Patent Literature

[Patent Literature 1] Japanese Patent No. 6335884

SITMMARY OF THE INVENTION Problems to Be Solved by the Invention

However, the emission intensity of the phosphor described in PatentLiterature 1 is unclear, and a phosphor with more favorable emissionintensity and a light-emitting device with favorable conversionefficiency are sought.

In view of the above-noted problems, in an aspect, the present inventiontakes as an objective to provide a light-emitting device, anillumination device, an image display device, and an indicator lamp fora vehicle having favorable color rendering, color reproducibility and/orfavorable conversion efficiency.

Solution to Problem

Upon thorough investigation, the present inventors have found that theabove-noted problems may be resolved by using a phosphor that includes acrystal phase represented by a specific composition and also has areflectance in a prescribed wavelength region or a difference or ratiobetween the reflectances in a plurality of prescribed wavelength regionsthat is a certain range, or by using a light-emitting device comprisingthe phosphor, and have perfected the present invention. Here, somenon-limiting embodiments of the present invention are shown below.

<1> A light-emitting device comprising a phosphor,

-   in which the phosphor includes a crystal phase having a composition    represented by formula [1] below, and-   a minimum reflectance in a prescribed wavelength region of the    phosphor is 20% or more, and the prescribed wavelength region is a    region from an emission peak wavelength of the phosphor to 800 nm.

(In formula [1] above,

-   MA includes one or more elements selected from a group consisting of    Sr, Ca, Ba, Na, K, Y, Gd, and La,-   MB includes one or more elements selected from a group consisting of    Li, Mg, and Zn,-   MC includes one or more elements selected from a group consisting of    Al, Si, Ga, In, and Sc,-   X includes one or more elements selected from a group consisting of    F, Cl, Br, and I,-   Re includes one or more elements selected from a group consisting of    Eu, Ce, Pr, Tb, and Dy, and-   a, b, c, d, e, and x satisfy the following expressions,    respectively.-   0.7 ≤ a ≤ 1.3-   0.7 ≤ b ≤ 1.3-   2.4 ≤ c ≤ 3.6-   3.2 ≤ d ≤ 4.8-   0.0 ≤ e ≤ 0.2-   (0.0 < x ≤ 0.2)

<2> A light-emitting device comprising a phosphor,

-   in which the phosphor includes a crystal phase having a composition    represented by formula [2] below, and-   a minimum reflectance in a prescribed wavelength region of the    phosphor is 20% or more, and the prescribed wavelength region is a    region from an emission peak wavelength of the phosphor to 800 nm.

(In formula [2] above,

-   MA includes one or more elements selected from a group consisting of    Sr, Ca, Ba, Na, K, Y, Gd, and La,-   MB includes one or more elements selected from a group consisting of    Li, Mg, and Zn,-   MC′ is Al,-   MD includes one or more elements selected from a group consisting of    Si, Ga, In, and Sc,-   X includes one or more elements selected from a group consisting of    F, Cl, Br, and I,-   Re includes one or more elements selected from a group consisting of    Eu, Ce, Pr, Tb, and Dy, and-   a, b, c, d, e, x, and y satisfy the following expressions,    respectively.-   0.7 ≤ a ≤ 1.3-   0.7 ≤ b ≤ 1.3-   2.4 ≤ c ≤ 3.6-   3.2 ≤ d ≤ 4.8-   0.0 ≤ e ≤ 0.2-   0.0 < x ≤ 0.2-   (0.0 < y ≤ 1.0)

<3> The light-emitting device according to <1> or <2>, in which informula [1] or formula [2], 80 mol% or more of MA is one or moreelements selected from a group consisting of Sr, Ca, and Ba.

<4> The light-emitting device according to <1> or <2>, in which informula [1] or formula [2], 80 mol% or more of MB is Li.

<5> The light-emitting device according to <1 >, in which in formula[1], 80 mol% or more of MC is constituted by one or more elementsselected from a group consisting of Al and Ga.

<6> The light-emitting device according to <5>, in which in formula [1],80 mol% or more of MC is Al.

<7> The light-emitting device according to <2>, in which in formula [2],80 mol% or more of MD is Ga.

<8> The light-emitting device according to <1> or <2>, in which informula [1] or formula [2], 80 mol% or more of Re is Eu.

<9> The light-emitting device according to <1> or <2>, in which a spacegroup of the crystal phase having a composition represented by formula[1] or formula [2] is P-1.

<10> The light-emitting device according to <1> or <2>, in which thephosphor has an emission peak wavelength in a range of 620 nm or moreand 660 nm or less in an emission spectrum.

<11> The light-emitting device according to <1> or <2>, in which thephosphor has a full width at half maximum (FWHM) in an emission spectrumof 70 nm or less.

<12> The light-emitting device according to <1> or <2>, furthercomprising a yellow phosphor and/or a green phosphor.

<13> The light-emitting device according to <12>, in which the yellowphosphor and/or green phosphor include at least one of a garnet typephosphor, a silicate type phosphor, a nitride phosphor, and anoxynitride phosphor.

<14> The light-emitting device according to <1> or <2> comprising afirst light emitter, and a second light emitter that emits visible lightdue to irradiation with light from the first light emitter, and thesecond light emitter comprises a phosphor that includes crystal phasehaving a composition represented by formula [1].

<15> An illumination device comprising the light-emitting deviceaccording to <14> as a light source.

<16> An image display device comprising the light-emitting deviceaccording to <14> as a light source.

<17> An indicator lamp for a vehicle comprising the light-emittingdevice according to <14> as a light source.

<18> A phosphor that includes a crystal phase having a compositionrepresented by formula [1] below, and

has a minimum reflectance in a prescribed wavelength region that is 20%or more, and the prescribed wavelength region is a region from anemission peak wavelength of the phosphor to 800 nm.

(In formula [1] above,

-   MA includes one or more elements selected from a group consisting of    Sr, Ca, Ba, Na, K, Y, Gd, and La,-   MB includes one or more elements selected from a group consisting of    Li, Mg, and Zn,-   MC includes one or more elements selected from a group consisting of    Al, Si, Ga, In, and Sc,-   X includes one or more elements selected from a group consisting of    F, Cl, Br, and I,-   Re includes one or more elements selected from a group consisting of    Eu, Ce, Pr, Tb, and Dy, and-   a, b, c, d, e, and x satisfy the following expressions,    respectively.-   0.7 ≤ a ≤ 1.3-   0.7 ≤ b ≤ 1.3-   2.4 ≤ c ≤ 3.6-   3.2 ≤ d ≤ 4.8-   0.0 ≤ e ≤ 0.2-   0.0 < x ≤ 0.2

<19> A phosphor that includes a crystal phase having a compositionrepresented by formula [2] below, and

has a minimum reflectance in a prescribed wavelength region that is 20%or more, and the prescribed wavelength region is a region from anemission peak wavelength of the phosphor to 800 nm.

(In formula [2] above,

-   MA includes one or more elements selected from a group consisting of    Sr, Ca, Ba, Na, K, Y, Gd, and La,-   MB includes one or more elements selected from a group consisting of    Li, Mg, and Zn,-   MC′ is Al,-   MD includes one or more elements selected from a group consisting of    Si, Ga, In, and Sc,-   X includes one or more elements selected from a group consisting of    F, Cl, Br, and I,-   Re includes one or more elements selected from a group consisting of    Eu, Ce, Pr, Tb, and Dy, and-   a, b, c, d, e, x, and y satisfy the following expressions,    respectively.-   0.7 ≤ a ≤ 1.3-   0.7 ≤ b ≤ 1.3-   2.4 ≤ c ≤ 3.6-   3.2 ≤ d ≤ 4.8-   0.0 ≤ e ≤ 0.2-   0.0 < x ≤ 0.2-   (0.0 < y ≤ 1.0)

<20> The phosphor according to <18> or <19>, in which in formula [1] orformula [2], 80 mol% or more of MA is one or more elements selected froma group consisting of Sr, Ca, and Ba.

<21> The phosphor according to <18> or <19>, in which in formula [1] orformula [2], 80 mol% or more of MB is Li.

<22> The phosphor according to <18>, in which in formula [1], 80 mol% ormore of MC is constituted by one or more elements selected from a groupconsisting of Al and Ga.

<23> The phosphor according to <22>, in which in formula [1], 80 mol% ormore of MC is Al.

<24> The phosphor according to <19>, in which in formula [2], 80 mol% ormore of MD is Ga.

<25> The phosphor according to <18> or <19>, in which in formula [1] orformula [2], 80 mol% or more of Re is Eu.

<26> The phosphor according to <18> or <19>, in which a space group ofthe crystal phase having a composition represented by formula [1] orformula [2] is P-1.

<27> The phosphor according to <18> or <19> having an emission peakwavelength in a range of 620 nm or more and 660 nm or less in anemission spectrum.

<28> The phosphor according to <18> or <19>, in which the full width athalf maximum (FWHM) in an emission spectrum is 70 nm or less.

Effect of the Invention

According to some embodiments of the present invention, a light-emittingdevice, an illumination device, an image display device, and/or anindicator lamp for a vehicle having favorable color rendering, colorreproducibility, and/or favorable conversion efficiency can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows XRD patterns of phosphors in example 1 and comparativeexample 1.

FIG. 2 shows emission spectra of the phosphors in example 1 andcomparative example 1.

FIG. 3 shows XRD patterns of phosphors in examples 4-10.

FIG. 4A shows emission spectra of the phosphors in comparative example 1and examples 4-9.

FIG. 4B shows emission spectra of the phosphors in comparative example 1and examples 10-12.

FIG. 5 shows normalized emission spectra of the phosphors in examples 4,5, and 9 and reference example 1.

FIG. 6A shows reflectance spectra of the phosphors in each of theexamples and the comparative example.

FIG. 6B shows reflectance spectra of the phosphors in each of theexamples.

FIG. 6C shows reflectance spectra of the phosphors in each of theexamples.

FIG. 6D shows reflectance spectra of the phosphors in each of theexamples.

FIG. 7A illustrates a relationship between the relative emissionintensity and a difference between the minimum reflectance in aplurality of specific wavelength regions.

FIG. 7B illustrates a relationship between the relative emissionintensity and a difference between the minimum reflectance in aplurality of specific wavelength regions.

FIG. 7C illustrates a relationship between the relative emissionintensity and a ratio between the minimum reflectance in a plurality ofspecific wavelength bands.

FIG. 7D illustrates a relationship between the relative emissionintensity and a ratio between the minimum reflectance in a plurality ofspecific wavelength bands.

FIG. 8A shows charts illustrating simulated light emissioncharacteristics of light-emitting devices in the examples.

FIG. 8B shows charts illustrating simulated light emissioncharacteristics of light-emitting devices in the examples.

FIG. 8C shows charts illustrating simulated light emissioncharacteristics of light-emitting devices in the examples.

FIG. 8D shows charts illustrating simulated light emissioncharacteristics of light-emitting devices in the examples.

FIG. 8E shows charts illustrating simulated light emissioncharacteristics of light-emitting devices in the examples.

FIG. 8F shows charts illustrating simulated light emissioncharacteristics of light-emitting devices in the examples.

FIG. 8G shows charts illustrating simulated light emissioncharacteristics of light-emitting devices in the examples.

DETAILED DESCRIPTION OF THE INVENTION

Hereafter, the present invention is described by way of embodiments andillustrative examples, however, the present invention is not limited tothe following embodiments, illustrative examples, or the like, and canbe implemented by making any desired modification within a scope thatdoes not exceed the substance of the present invention.

Note that in the present specification, a numerical range representedusing “-” signifies a range containing the numerical values noted beforeand after the “-” as a lower limit value and an upper limit value. Inaddition, for composition formulas of phosphors in the presentspecification, the end of each composition formula is represented by acomma (,). In addition, where a plurality of elements are listedseparated by a comma (,), this indicates that one or two or more of thelisted elements may be contained in any combination and composition. Forexample, the composition formula “(Ca, Sr, Ba)Al₂O₄:Eu” inclusivelyindicates all of “CaAl₂O₄:Eu”, “SrA1₂O₄:Eu”, “BaAl₂O₄:Eu”,“Ca₁-_(x)Sr_(x)Al₂O₄:Eu”, “Sr₁-_(x)Ba_(x)Al₂O₄:Eu”,“Ca₁-_(x)Ba_(x)Al₂O₄:Eu”, and “Ca₁-_(x)-_(y)Sr_(x)Ba_(y)Al₂O₄:Eu” (where0 < x < 1, 0 < y < 1, and 0 < x + y < 1 in the formula).

Phosphor

In one embodiment, the present invention is a phosphor that includes acrystal phase having a composition represented by the following formula[1], and is a phosphor having a minimum reflectance in a wavelengthregion from the emission peak wavelength of the phosphor to 800 nm thatis 20% or more (which hereafter may be referred to as “phosphor [1] ofthe present embodiment,” and phosphor [1] of the present embodiment anda phosphor [2] of the present embodiment, described later, maycollectively be referred to as “phosphors of the present embodiment”).In another embodiment, the present invention is a light-emitting devicecomprising the phosphor [1] of the present embodiment.

(In formula [1] above,

-   MA includes one or more elements selected from a group consisting of    Sr, Ca, Ba, Na, K, Y, Gd, and La,-   MB includes one or more elements selected from a group consisting of    Li, Mg, and Zn,-   MC includes one or more elements selected from a group consisting of    Al, Si, Ga, In, and Sc,-   X includes one or more elements selected from a group consisting of    F, Cl, Br, and I,-   Re includes one or more elements selected from a group consisting of    Eu, Ce, Pr, Tb, and Dy, and-   a, b, c, d, e, and x satisfy the following expressions,    respectively.-   0.7 ≤ a ≤ 1.3-   0.7 ≤ b ≤ 1.3-   2.4 ≤ c ≤ 3.6-   3.2 ≤ d ≤ 4.8-   0.0 ≤ e ≤ 0.2-   (0.0 < x ≤ 0.2)

In formula [1], europium (Eu), cerium (Ce), praseodymium (Pr), neodymium(Nd), samarium (Sm), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium(Er), thulium (Tm), and ytterbium (Yb), and the like can be used for Re,but in terms of improving emission wavelength and emission quantumefficiency, Re preferably includes one or more elements selected from agroup consisting of Eu, Ce, Pr, Tb, and Dy, more preferably includes Eu,still more preferably 80 mol% or more of Re is Eu, and further stillmore preferably Re is Eu.

In formula [1], MA includes one or more elements selected from a groupconsisting of calcium (Ca), strontium (Sr), barium (Ba), sodium (Na.),potassium (K), yttrium (Y), gadolinium (Gd), and lanthanum (La),preferably includes one or more elements selected from a groupconsisting of Ca, Sr, and Ba, and more preferably MA includes Sr. Inaddition, preferably, 80 mol% or more of MA is constituted by theabove-noted preferred elements, and more preferably MA is constituted bythe above-noted preferred elements.

In formula [1], MB includes one or more elements selected from a groupconsisting of lithium (Li), magnesium (Mg), and zinc (Zn), preferablyincludes Li, more preferably 80 mol% or more of MB is Li, and still morepreferably MB is Li.

In formula [1], MC includes one or more elements selected from a groupconsisting of aluminum (Al), silicon (Si), gallium (Ga), indium (In),and scandium (Sc), preferably includes Al, Ga, or Si, more preferablyincludes one or more elements selected from a group consisting of Al andGa, still more preferably 80 mol% or more of MC is constituted by one ormore elements selected from a group consisting of Al and Ga, especiallypreferably 90 mol% or more of MC is constituted by one or more elementsselected from a group consisting of Al and Ga, and most preferably MC isconstituted by one or more elements selected from a group consisting ofAl and Ga.

In one embodiment, 80 mol% or more of MC is Al, preferably 90 mol% ormore, more preferably 95 mol% or more, and still more preferably 98 mol%or more. By 80 mol% or more of MC being Al, a red phosphor exhibiting asimilar emission peak wavelength and emission intensity as existing redphosphors such as S/CASN and with a narrow full width at half maximumcan be provided, and by using such a red phosphor, a light-emittingdevice can be provided that has superior color rendering or colorreproducibility while maintaining conversion efficiency (lm/W) similarto or better than the conventional.

In formula [1], N represents nitrogen. N may be partially substitutedwith oxygen (O) in order to maintain the charge balance of the overallcrystal phase, or in order to adjust the emission peak wavelength.

In formula [1], X includes one or more elements selected from a groupconsisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).That is, in a specific embodiment, in terms of stabilization of acrystal structure and maintaining a charge balance for the entirephosphor, a portion of N may be substituted with the above-mentionedhalogen elements represented by X.

Formula [1] includes cases where a component other than those specifiedabove is included in trace amounts unavoidably, unintentionally, orderiving from trace additive components or the like.

Examples of a component other than those specified above include anelement having an element number that is one different from an elementthat was intentionally added, an element of the same group as an elementthat was intentionally added, a rare earth element different from a rareearth element that was intentionally added, and a halogen element when ahalogen compound was used for an Re raw material, an element that maygenerally be included in various other raw materials as an impurity, orthe like.

An example of a case where a component other than those specified aboveis included unavoidably or unintentionally may be, for example, a casewhere the component derives from an impurity in the raw material andwhere the component is introduced in a manufacturing process such as apulverization step or synthesis step. In addition, examples of the traceadditive component may include a reaction assistant, Re raw material,and the like.

In formula [1] above, a, b, c, d, e, and x respectively indicate molarcontent of MA, MB, MC, N, X, and Re contained in a phosphor.

The value of a is ordinarily 0.6 or more, preferably 0.7 or more, morepreferably 0.8 or more, and still more preferably 0.9 or more, and isordinarily 1.4 or less, preferably 1.3 or less, more preferably 1.2 orless, and still more preferably 1.1 or less.

The value of b is ordinarily 0.6 or more, preferably 0.7 or more, morepreferably 0.8 or more, and still more preferably 0.9 or more, and isordinarily 1.4 or less, preferably 1.3 or less, more preferably 1.2 orless, and still more preferably 1.1 or less.

The value of c is ordinarily 2.1 or more, preferably 2.4 or more, morepreferably 2.6 or more, and still more preferably 2.8 or more, and isordinarily 3.9 or less, preferably 3.6 or less, more preferably 3.4 orless, and still more preferably 3.2 or less.

The value of d is ordinarily 3 or more, preferably 3.2 or more, morepreferably 3.4 or more, still more preferably 3.6 or more, and even morepreferably 3.8 or more, and is ordinarily 5 or less, preferably 4.8 orless, more preferably 4.6 or less, still more preferably 4.4 or less,and even more preferably 4.2 or less.

The value of e is not particularly limited, but is ordinarily 0 or more,and is ordinarily 0.2 or less, preferably 0.1 or less, more preferably0.06 or less, still more preferably 0.04 or less, and even morepreferably 0.02 or less.

The value of x is ordinarily a value greater than 0, preferably 0.0001or more, and more preferably 0.001 or more, and is ordinarily 0.2 orless, preferably 0.15 or less, more preferably 0.12 or less, still morepreferably 0.1 or less, and even more preferably 0.08 or less.

When the value of x is a value equal to or greater than the above-notedlower limit or higher than the above-noted lower limit, a phosphorhaving favorable emission intensity can be obtained, and when the valueof x is equal to or less than the above-noted upper limit, Re can befavorably incorporated in a crystal and a phosphor can be obtained thatreadily functions as an emission center.

When b, c, d, and e are in the above-noted ranges, a crystal structurestabilizes. In addition, the values of d and e can be adjusted somewhatwith the objective of maintaining a charge balance for the entirephosphor.

Also, when the value of a is in the above-noted range, a crystalstructure stabilizes and a phosphor with few heterogeneous phases can beobtained.

The value of b + c is ordinarily 3.1 or more, preferably 3.4 or more,and more preferably 3.7 or more, and is ordinarily 4.9 or less,preferably 4.6 or less, and more preferably 4.3 or less.

When the value of b + c is in the above-noted range, a crystal structurestabilizes.

The value of d + e is ordinarily 3.2 or more, preferably 3.4 or more,and more preferably 3.7 or more, and is ordinarily 5.0 or less,preferably 4.6 or less, and more preferably 4.3 or less.

When the value of d + e is in the above-noted range, a crystal structurestabilizes.

When all values are in the above-noted ranges, the resulting phosphorhas a favorable emission peak wavelength and full width at half maximumof an emission spectrum, which is preferred.

Note that a method of specifying an elemental composition of thephosphor is not particularly limited, and can be found with a routinemethod. For example, specification can be performed with GD-MS, ICPspectroscopy, an energy-dispersive X-ray spectrometer (EDX), or thelike.

In one embodiment, the present invention is a phosphor that includes acrystal phase having a composition represented by the following formula[2], and is a phosphor having a minimum reflectance in a wavelengthregion from the emission peak wavelength of the phosphor to 800 nm thatis 20% or more (which hereafter may be referred to as “phosphor [2] ofthe present embodiment”).

In addition, in another embodiment, the present invention is alight-emitting device comprising the phosphor [2] of the presentembodiment.

(In formula [2] above,

-   MA includes one or more elements selected from a group consisting of    Sr, Ca, Ba, Na, K, Y, Gd, and La,-   MB includes one or more elements selected from a group consisting of    Li, Mg, and Zn,-   MC′ is Al,-   MD includes one or more elements selected from a group consisting of    Si, Ga, In, and Sc,-   X includes one or more elements selected from a group consisting of    F, Cl, Br, and I,-   Re includes one or more elements selected from a group consisting of    Eu, Ce, Pr, Tb, and Dy, and-   a, b, c, d, e, x, and y satisfy the following expressions,    respectively.-   0.7 ≤ a ≤ 1.3-   0.7 ≤ b ≤ 1.3-   2.4 ≤ c ≤ 3.6-   3.2 ≤ d ≤ 4.8-   0.0 ≤ e ≤ 0.2-   0.0 < x ≤ 0.2-   (0.0 < y ≤ 1.0)

The type and structure of the elements MA, MB, N, X, and Re in formula[2] can be configured similarly to formula [1].

MC is Al.

MD includes one or more elements selected from a group consisting of Si,Ga, In, and Sc, and in terms of improving crystal stability and emissionintensity, preferably includes one or more elements selected from agroup consisting of Ga and Si, and more preferably includes Ga, andstill more preferably 80 mol% or more of MD is Ga, and especiallypreferably MD is Ga.

The values and preferred ranges of a, b, c, d, e, and x in formula [2]can be configured similarly to formula [1].

The value of y in formula [2] is greater than 0.0, and is ordinarily0.01 or more, preferably 0.015 or more, more preferably 0.03 or more,still more preferably 0.05 or more, and especially preferably 0.10 ormore, and is ordinarily 1.00 or less, preferably 0.70 or less, morepreferably 0.50 or less, still more preferably 0.30 or less, andespecially preferably 0.25 or less.

When the value of y is equal to or greater than the lower limit, theemission peak wavelength of the phosphor is shortened, and by using sucha phosphor, a light-emitting device can be provided having favorablecolor rendering or color reproducibility. In addition, when the value ofy is equal to or less than the upper limit, a phosphor having favorableemission intensity can be obtained, and by using such a phosphor, alight-emitting device can be provided having favorable conversionefficiency. The value of y can be adjusted as appropriate in order toobtain the desired emission intensity and emission peak wavelength foran objective.

Particle Size of Crystal Phase

The particle size of the crystal phase of the phosphor according to thepresent embodiment is ordinarily 2 µm or more and 35 µm or less for avolume median particle size, the lower limit value is preferably 3 µm,more preferably 4 µm, and still more preferably 5 µm, and the upperlimit value is preferably 30 µm or less, more preferably 25 µm or less,still more preferably 20 µm, and especially preferably 15 µm.

The volume median particle size being equal to or greater than theabove-noted lower limit is preferable in terms of improving lightemission characteristics the crystal phase exhibits in an LED package,and the volume median particle size being equal to or less than theabove-noted upper limit is preferable in terms of the crystal phasebeing able to avoid obstructing a nozzle in an LED package manufacturingstep.

The volume median particle size of the crystal phase of a phosphor canbe measured with technique known to those skilled in the art, but in apreferable embodiment, for example, it can be measured with laserdiffraction particle size analyzer. In this example, the volume medianparticle size (d₅₀) is defined as the size of the particle when thecumulative number of particles which is counted sequentially from thesmallest one becomes half of the total number.

Phosphor Properties and the Like Space Group

A crystal system (space group) of the phosphor of the present embodimentis more preferably P-1. So long as a statistically average structureexhibits a repeating period of the above-noted length in a range thatmay be demarcated by powder X-ray diffraction or single crystal X-raydiffraction, the space group of the phosphor of the present embodimentis not particularly limited, but preferably belongs to #2, which isbased on “International Tables for Crystallography (third, revisededition), Volume A, Space-group Symmetry”.

With the above space group, a full width at half maximum (FWHM) in theemission spectrum becomes narrower and a phosphor having good emissionefficiency can be obtained.

In this example, the space group can be found according to a routinemethod, for example with electron beam diffraction, X-ray diffractionstructure analysis using powder or single crystal, neutron beamdiffraction structure analysis, and the like.

When the intensity of a peak that appears in a region where 2θ = 38-39°in a powder X-ray diffraction spectrum of the phosphor of the presentembodiment is designated Ix and the intensity of a peak that appears ina region where 2θ = 37-38° is designated Iy, the relative intensityIx/Iy of Ix where Iy is treated as 1 is preferably 0.140 or less, morepreferably 0.120 or less, still more preferably 0.110 or less, even morepreferably 0.080 or less, especially preferably 0.060 or less, and mostespecially preferably 0.040 or less, and is ordinarily 0 or more, butthe smaller the better.

The peak in the region where 2θ = 37-38° is one characteristic peak thatis observed when a crystal system (space group) is P-1, and when Iy isrelatively high, a phosphor having greater P-1 phase purity can beobtained. By Ix/Iy being equal to or less than the above-noted upperlimit, a phosphor has high phase purity and a narrow full width at halfmaximum (FWHM), and therefore emission efficiency of a light-emittingdevice improves.

Reflectance in Specific Wavelength Band

In one embodiment, the phosphor of the present embodiment has a minimumreflectance (hereafter also denoted as A%) in a prescribed wavelengthregion that is ordinarily 20% or more, and the prescribed wavelengthregion is a region from the emission peak wavelength of the phosphor to800 nm. The minimum reflectance is preferably 25% or more, morepreferably 30% or more, still more preferably 35% or more, especiallypreferably 50% or more, more especially preferably 60% or more, andextremely preferably 70% or more.

The upper limit of the reflectance is not particularly limited, but thehigher the better, and is ordinarily 100% or less. When the reflectanceis equal to or greater than the above-noted lower limit, a red phosphorhaving superior emission intensity or quantum efficiency can beprovided, and by using such a phosphor, a light-emitting device havingfavorable conversion efficiency can be provided.

In one embodiment, the prescribed wavelength region associated with thereflectance A (%) of the phosphor of the present embodiment is awavelength region from the emission peak wavelength to 800 nm. Reasonsfor selecting the above-noted wavelength band when stipulating thereflectance of the phosphor of the present embodiment are describedbelow.

The present inventors have made the following findings:

-   1. A portion of the phosphors having a crystal phase represented by    formula [1] or [2] above appear to have a slightly grayish cast when    the body color of the phosphor in powder form was checked by eye    under natural light in an unexcited state. In the present    specification, this state may also be expressed as “dull” or having    “dullness.”-   2. Among the phosphors having a crystal phase represented by formula    [1] or [2] above, a phosphor having little of the above-noted    “dullness” has superior emission intensity or quantum efficiency,    and by using such a phosphor, a light-emitting device having    favorable conversion efficiency can be provided.-   3. Among the phosphors having a crystal phase represented by formula    [1] or [2] above, a phosphor having little of the above-noted    “dullness” tends to have high reflectance overall, and in particular    is defined by reflectance to light in a specific wavelength band, or    defined by an index that includes reflectance to light in the    specific wavelength band, and can thereby be specified accurately.

Ordinarily, the specific wavelength band is preferably a wavelengthbelonging to a wavelength band different from an excitation spectrumregion.

From one vantage point, the specific wavelength band is preferably awavelength in a wavelength region equal to or greater than the emissionpeak wavelength and equal to or less than an end portion of along-wavelength side of the emission spectrum.

In a specific embodiment, a wavelength equal to or greater than theemission peak wavelength and equal to or less than 900 nm can ordinarilybe selected as the specific wavelength band, and the upper limit ispreferably 800 nm or less and more preferably 780 nm or less. Asnecessary, the wavelength region can occupy any wavelength band that isequal to or greater than the lower limit and equal to or less than theupper limit noted above.

The wavelength region of excitation spectrum of the phosphor of thepresent embodiment is primarily 300 nm-520 nm, but absorption may occurnear 600 run as well. In this example, it is inappropriate to define thebody color of the phosphor based only on the reflectance of thewavelength region of the excitation spectrum because, in that case, thephosphor absorbs incident light and reflectance is influenced by theabsorption rate.

From the above perspective, when defining the phosphor of the presentembodiment by reflectance, the body color of the phosphor can beaccurately defined by reflectance of the wavelength band that is littleaffected by absorption by the phosphor, or by employing a parameterrelated to this reflectance.

In one embodiment, for the phosphor of the present embodiment, when theminimum reflectance in a wavelength region from the emission peakwavelength Wp (nm) to [Wp - 50] (nm) is designated as B%, the value of[A - B] for the difference from the reflectance A (%) is preferably -1.5points or more, more preferably 0.0 points or more, still morepreferably 3.0 points or more, and especially preferably 4.0 points ormore. The upper limit of [A - B] is not particularly limited, but isordinarily 50.0 points or less.

When the value of [A - B] is equal to or greater than the above-notedlower limit, a phosphor having high emission intensity can be obtained,and by using such a phosphor, a light-emitting device having highconversion efficiency can be provided.

It is unclear why a phosphor with high emission intensity is obtainedwhen [A - B] is a high value, but for example, there is no lightabsorption by the Re element (activator element) in a wavelength bandequal to or higher than the emission peak wavelength associated with thereflectance A (%), and therefore absorptivity being low and reflectancebeing high may be considered desirable, while in turn, the reflectance B(%) shows absorption of light by the Re element (activator element) andthe higher the absorptivity, the more reflectance is reduced. Therefore,it is possible that when the value of [A - B] is large, the activatorelement absorption of light contributing to emission is high and thus aphosphor having high emission intensity can be obtained. In this case,the wavelength regions associated with the reflectances A (%) and B (%)are consecutive, and therefore it is highly likely that A (%) and B (%)are comparatively close values, and as a result, defining the phosphorby comparison of A (%) and B (%), rather than B (%) alone, may beconsidered preferable.

In one embodiment, for the phosphor of the present embodiment, when theminimum reflectance in a wavelength region from 400 nm to 550 nm isdesignated as C%, the value of [A - C] for the difference from thereflectance A (%) is preferably 0.0 points or more, more preferably 2.0points or more, still more preferably 5.0 points or more, especiallypreferably 10.0 points or more, more especially preferably 15.0 pointsor more, and extremely preferably 20.0 points or more. The upper limitof [A - C] is not particularly limited, but is ordinarily 50.0 points orless.

When the value of [A - C] is equal to or greater than the above-notedlower limit, a phosphor having high emission intensity can be obtained,and by using such a phosphor, a light-emitting device having highconversion efficiency can be provided.

In one embodiment, for the phosphor of the present embodiment, when theminimum reflectance in the wavelength region from 400 nm to 550 nm isdesignated as C%, the value of C/A. for the ratio to the reflectance A(%) is preferably 1.05 or less, more preferably 1.00 or less, still morepreferably 0.90 or less, especially preferably 0.80 or less, and moreespecially preferably 0.75 or less. The lower limit of C/A is notparticularly limited, but is ordinarily 0.0 or more.

When the value of C/A is equal to or less than the above-noted upperlimit, a phosphor having high emission intensity can be obtained, and byusing such a phosphor, a light-emitting device having high conversionefficiency can be provided.

It is unclear why a phosphor with high emission intensity is obtainedwhen [A - C] is a high value or C/A is a low value, but for example,there is very little absorption of light contributing to emission in awavelength band equal to or higher than the emission peak wavelengthassociated with the reflectance A (%), and therefore absorptivity beinglow and reflectance being high may be considered desirable, while inturn, the wavelength band associated with the reflectance C (%) is awavelength band that often uses blue light in an excitation lightsource, and the higher the absorptivity, the more reflectance isreduced. Therefore, it is possible that a phosphor with a lowreflectance C (%) has high absorption of excitation light contributingto emission and thus a phosphor having high emission intensity can beobtained, or the like.

Note that, as may also be understood from the examples below, a phosphorwith high absorption that does not contribute to emission due toimpurities or the like tends to have reflectance that decreases overallin a broad wavelength band, and therefore from the above-notedperspective, when specifying a phosphor, defining the phosphor bycomparison of A (%) and C (%), rather than C (%) alone, may beconsidered preferable.

Emission Spectrum Characteristics

The phosphor according to the present embodiment is excited byirradiating the phosphor with light having a suitable wavelength andgives off a red light exhibiting a favorable emission peak wavelengthand full width at half maximum (FWHM) in the emission spectrum.Hereafter, the emission spectrum as well as an excitation wavelength,emission peak wavelength, and full width at half maximum (FWHM) aredescribed.

Excitation Wavelength

The phosphor of the present embodiment has an excitation peak in awavelength range of 270 nm or more ordinarily, preferably 300 nm ormore, more preferably 320 nm or more, still more preferably 350 nm ormore, and especially preferably 400 nm or more, and ordinarily 500 nm orless, preferably 480 nm or less, and more preferably 460 nm or less.That is, the phosphor is excited by light in a region from ultravioletto blue.

Note that descriptions of the shape of the emission spectrum, as well asof the full width at half maximum and the emission peak wavelength beloware applicable regardless of excitation wavelength, but in terms ofimproving quantum efficiency, irradiation with light having a wavelengthin the above-noted range with good absorption and excitation efficiencyis preferable.

Emission Peak Wavelength

The phosphor of the present embodiment has a peak wavelength in theemission spectrum of 620 nm or more ordinarily, preferably 625 nm ormore, and more preferably 630 nm or more. In addition, the peakwavelength in the emission spectrum is ordinarily 670 nm or less,preferably 660 nm or less, and more preferably 655 nm or less.

When the peak wavelength in the emission spectrum of the phosphor is inthe above-noted range, the color of the emitted light is a favorable redcolor, and by using this, a light-emitting device can be provided havinggood color rendering or color reproducibility. In addition, when thepeak wavelength in the emission spectrum of the phosphor is equal to orlower than the above-noted upper limit, a light-emitting device can beprovided having favorable luminous efficiency of the red color, andfavorable luminous efficacy in Im/W.

Phosphors having different peak wavelengths according to usage can beused in the light-emitting device. A method for obtaining phosphors withdifferent peak wavelengths is not particularly limited, and can beachieved by changing the configuration of the MC element, as an exampleof one method.

In one embodiment, a phosphor having a long emission peak wavelength canbe obtained by using Al for MC in formula [1] and increasing theproportion of Al. In this embodiment, the emission peak wavelength ispreferably 640 run or more, and more preferably 645 nm or more, and isordinarily 670 nm or less, and preferably 660 nm or less. By providing aphosphor with an emission wavelength in this range, a light-emittingdevice used for illumination, for example, can be provided that achievesboth emission efficiency and color rendering, or a light-emitting deviceused in a backlight component of a liquid crystal display can beprovided that achieves both emission efficiency and a color reproductionrange.

In another embodiment, a phosphor can be obtained that has a relativelyshort emission peak wavelength by providing a phosphor that includes acrystal phase having a composition represented by formula [2] using MC′(Al) and an MD element. In this embodiment, the emission peak wavelengthis ordinarily 615 nm or more, preferably 620 nm or more, more preferably625 nm or more, and still more preferably 630 nm or more, and isordinarily 660 nm or less, preferably 645 nm or less, and morepreferably 640 nm or less. A light-emitting device having good colorrendering or color reproducibility can be obtained by providing aphosphor having an emission wavelength in the above-noted range.

Full Width at Half Maximum of Emission Spectrum

The phosphor of the present embodiment has a full width at half maximumof the emission peak in the emission spectrum that is ordinarily 80 nmor less, preferably 70 nm or less, more preferably 60 run or less, stillmore preferably 55 nm or less, and especially preferably 50 nm or less,and is ordinarily 10 nm or more.

A color reproduction range of an image display device such as a liquidcrystal display can be broadened without reducing color purity by usingthe phosphor having the full width at half maximum of the emission peakwithin the above-noted range.

In addition, a phosphor having relatively high luminous efficiency ofthe emission wavelength region can be obtained by having the emissionpeak wavelength and the full width at half maximum equal to or less thanthe above-noted upper limits, and a light-emitting device having highconversion efficiency can be provided by using such a phosphor in alight-emitting device.

Note that a GaN type LED, for example, can be used to excite thephosphor with light of around 450 nm wavelength. In addition, theemission spectrum of the phosphor can be measured, and the emission peakwavelength, peak relative intensity, and peak full width at half maximumthereof be calculated, using a commercially-available spectrometrydevice such as a fluorescence spectrophotometer comprising a genericphotodetector and a light source having an emission wavelength of300-400 nm, such as a commercially available xenon lamp, for example.

Method for Manufacturing Phosphor

The phosphor of the present embodiment can be synthesized by mixing andheating raw materials of each element comprising the phosphor such thatthe proportions of each element fulfill formula [1] or [2].

Raw Material

The raw material of each element (MA, MB, MC, MC′, MD, and Re) are notparticularly limited, and examples may include the element alone, anoxide, a nitride, a hydroxide, a chloride, a halide such as fluoride, aninorganic salt such as sulfate, nitrate, or phosphate, an organic saltsuch as acetate, and the like. Besides these, a compound containing twoor more of the element groups may be used. In addition, each compoundmay also be a hydrate or the like. Note that in the examples below,Sr₃N₂, Li₃N, AlN, GaN, and EuF₃ or Eu₂O₃ were used as startingmaterials.

A method of acquiring each of the raw materials is not particularlylimited and can employ purchasing commercially available materials.

The purity of each of the raw materials is not particularly limited, butin terms of strict adherence to element ratios, and avoiding theoccurrence of a heterogeneous phase due to an impurity, higher puritiesare more preferred, ordinarily 90 mol% or more, preferably 95 mol% ormore, more preferably 97 mol% or more, and still more preferably 99 mol%or more, and the upper limit is not particularly limited, but isordinarily 100 mol% or less, and impurities that are unavoidably mixedin may be included.

In the examples described below, raw materials all having 95 mol% purityor more were used.

The oxygen element (O), nitrogen element (N), and halogen element (X)can be supplied using an oxide, nitride, and halide or the like as theraw material for each of the elements, but can also be introduced byusing an oxygen- or nitrogen-containing atmosphere during a synthesisreaction.

Mixing Step

The method of mixing the raw materials is not particularly limited andcan employ a routine method. For example, phosphor raw materials areweighed so as to achieve a target composition and are sufficiently mixedusing a ball mill or the like, obtaining a phosphor raw materialmixture. The above mixing procedure is not particularly limited, butprocedures (a) and (b) below are provided as specific examples.

-   (a) A dry mixing method that combines pulverization using a mortar    and pestle, or a dry pulverizer such as a hammer mill, roll mill,    ball mill, or jet mill, for example, and mixing using a mortar and    pestle, or a mixer such as a ribbon blender, V blender, or Henschel    mixer, for example, and pulverizes and mixes the above-noted    phosphor raw materials.-   (b) A wet mixing method in which a dispersion medium or a solvent    such as water is added to the above-noted phosphor raw materials,    the materials are mixed using a pulverizer, mortar and pestle, or    evaporating dish and stirring rod, for example, and once rendered    into a solution or slurry state, the materials are dried by spray    drying, heat drying, air drying, or the like.

Mixing of the phosphor raw materials may be either the dry mixing methodor wet mixing method noted above, but in order to avoid contamination ofthe phosphor raw materials by moisture, a dry mixing method or a wetmixing method using a non-aqueous solvent is preferred.

Note that the method of (a) was adopted in the examples described below.

Heating Step

In the heating step, for example, the phosphor raw material mixtureobtained in the mixing step is placed in a crucible and is continuouslyheated at a temperature of 500° C.-1200° C., preferably 600° C.-1000°C., and more preferably 700-950° C.

The material of the crucible preferably does not react with the phosphorraw materials or a reaction product, and examples may include alumina,quartz, ceramics such as boron nitride, silicon carbide, and siliconnitride, metals such as nickel, platinum, molybdenum, tungsten,tantalum, niobium, iridium, and rhodium, or an alloy with these as aprincipal component, or the like.

Note that a boron nitride crucible was used in the examples describedbelow.

Heating is preferably performed in an inert atmosphere, and can use agas with nitrogen, argon, helium, or the like as a principal component.

Note that heating was carried out in a nitrogen atmosphere in theexamples described below.

In the heating step, in the above-noted temperature zone, heating iscarried out ordinarily for 10 minutes-200 hours, preferably 1-100 hours,and more preferably 3-50 hours. In addition, the heating step may beperformed one time or may be performed multiple times. Examples of anaspect in which the heating is performed multiple times may include anaspect including an annealing step by heating the phosphor underpressure in order to repair defects, an aspect in which primary heatingobtaining primary particles or an intermediate product is performed,after which secondary heating obtaining secondary particles or a finalproduct is performed, or the like.

The phosphor of the present embodiment is obtained in this way.

Selection of Phosphor

The phosphor of the present embodiment can generally be obtained withthe above method, but sometimes the phosphor particles partially containsuch ones that deviate slightly from the preferred properties due toslight differences such as minute accretion within a reaction vessel,impurities in the various reagents, the lot of the various raw materialreagents, and the like, and there are cases where phosphors with largeand small particle sizes, phosphors with different reflectance or thelike, and the like are mixed together.

Therefore, the phosphor of the present embodiment can be obtainedreliably by, for example, changing a number of conditions to manufacturea phosphor, selecting the resulting phosphor by classification, washing,and the like, analyzing the reflectance, XRD spectrum, and the like, andselecting a phosphor satisfying the requirements of above embodiments.

Light-Emitting Device

In one embodiment, the present invention is a light-emitting device thatincludes a first light emitter (excitation light source) and a secondlight emitter that emits visible light due to irradiation with lightfrom the first light emitter, the light-emitting device including, asthe second light emitter, the phosphor of the present embodiment whichincludes a crystal phase having a composition represented by formula [1]or [2] above. In this example, one kind of second light emitter may beused singly, or two or more kinds may be used together in anycombination and ratio.

As the second light emitter, the light-emitting device of the presentembodiment comprises the phosphor of the present embodiment whichincludes a crystal phase having a composition represented by formula [1]or [2] above, but also can use a phosphor that emits fluorescence fromyellow through green and red (orange through red) regions underirradiation with light from the excitation light source.

In a specific embodiment, the light-emitting device of the presentinvention comprises a phosphor including a crystalline phase having acomposition represented by the formula [1] or [2] above and furthercomprising a yellow phosphor and/or green phosphor.

Specifically, when configuring a light-emitting device, a phosphorhaving an emission peak in a wavelength range of 550 nm or more and 600nm or less is preferred as a yellow phosphor, and a phosphor having anemission peak in a wavelength range of 500 nm or more and 560 nm or lessis preferred as a green phosphor. In addition, an orange through redphosphor has an emission peak in a wavelength range that is ordinarily615 nm or more, preferably 620 run or more, more preferably 625 nm ormore, and still more preferably 630 run or more, and is ordinarily 660nm or less, preferably 650 nm or less, more preferably 645 nm or less,and still more preferably 640 nm or less.

A light-emitting device exhibiting superior color reproducibility can beprovided by appropriately combining phosphors with the above-notedwavelength bands. Note that an excitation light source having anemission peak in a wavelength range less than 420 nm may be used.

Hereafter, an aspect of the light-emitting device is described in a casewhere, as the red phosphor, the light-emitting device uses the phosphorof the present embodiment having an emission peak in the wavelengthrange of 620 nm or more and 660 nm or less and including a crystal phasehaving a composition represented by formula [1] or [2] above, and uses afirst light emitter having an emission peak in the wavelength range of300 nm or more and 460 nm or less. However, the present embodiment isnot limited to these.

In the above-noted case, the light-emitting device of the presentembodiment can be configured as the following aspects (A), (B), or (C),for example.

-   (A) An aspect using, as a first light emitter, a light emitter    having an emission peak in a wavelength range of 300 nm or more and    460 nm or less and, as a second light emitter, using at least one    kind of phosphor having an emission peak in a wavelength range of    550 nm or more and 600 nm or less (yellow phosphor) and the phosphor    of the present embodiment that includes a crystal phase having a    composition represented by [1] or [2] above.-   (B) An aspect using, as a first light emitter, a light emitter    having an emission peak in a wavelength range of 300 nm or more and    460 nm or less and, as a second light emitter, using at least one    kind of phosphor having an emission peak in a wavelength range of    500 nm or more and 560 nm or less (green phosphor) and the phosphor    of the present embodiment that includes a crystal phase having a    composition represented by [1] or [2] above.-   (C) An aspect using, as a first light emitter, a light emitter    having an emission peak in a wavelength range of 300 nm or more and    460 nm or less and, as a second light emitter, using at least one    kind of phosphor having an emission peak in a wavelength range of    550 nm or more and 600 nm or less (yellow phosphor), at least one    kind of phosphor having an emission peak in a wavelength range of    500 nm or more and 560 nm or less (green phosphor), and the phosphor    of the present embodiment that includes a crystal phase having a    composition represented by [1] or [2] above.

A commercially available phosphor can be used as the green or yellowphosphor in the above aspects, and a garnet type phosphor, silicate typephosphor, nitride phosphor, oxynitride phosphor, and the like can beused, for example.

Yellow Phosphor

Examples of the garnet type phosphor that can be used for the yellowphosphor may include, for example, (Y, Gd, Lu, Tb, La)₃(Al, Ga)₅O₁₂:(Ce,Eu, Nd), examples of the silicate type phosphor may include, forexample, (Ba, Sr, Ca, Mg)₂SiO₄:(Eu, Ce), examples of the nitridephosphor and oxynitride phosphor may include, for example, (Ba, Ca,Mg)Si₂O₂N₂:Eu (SION type phosphor), (Li, Ca)₂(Si, Al)₁₂(O, N)₁₆:(Ce, Eu)(α-sialon phosphor), (Ca, Sr)AlSi₄(O, N)₇:(Ce, Eu) (1147 phosphor), (La,Ca, Y, Gd)₃(Al, Si)₆N₁₁:(Ce, Eu) (LSN phosphor), and the like.

One kind of these may be used singly, or two or more kinds may be usedin combination.

As a yellow phosphor, a garnet type phosphor is preferred for theabove-noted phosphor, and of these, a YAG type phosphor represented byY₃Al₅O₁₂:Ce is most preferred.

Green Phosphor

Examples of the garnet type phosphor that can be used for the greenphosphor may include, for example, (Y, Gd, Lu, Tb, La)₃(Al, Ga)₅O₁₂:(Ce,Eu, Nd) and Ca₃(Sc, Mg)₂Si₃O₁₂:(Ce, Eu) (CSMS phosphor), examples of thesilicate type phosphor may include, for example, (Ba, Sr, Ca,Mg)₃SiO₁₀:(Eu, Ce) and (Ba, Sr, Ca, Mg)₂SiO₄:(Ce, Eu) (BSS phosphor),examples of the oxide phosphor may include, for example, (Ca, Sr, Ba,Mg)(Sc, Zn)₂O_(4:)(Ce, Eu) (CASO phosphor), examples of the nitridephosphor and oxynitride phosphor may include, for example, (Ba, Sr, Ca,Mg)Si₂O₂N₂:(Eu, Ce), Si_(6-z)Al_(z)O_(z)N_(8-z):(Eu, Ce) (β-sialonphosphor) (0 < z ≤ 1), and (Ba, Sr, Ca, Mg, La)₃(Si,Al)₆O₁₂N₂:(Eu, Ce)(BSON phosphor), and examples of the aluminate phosphor may include, forexample, (Ba, Sr, Ca, Mg)₂Al₁₀O₁₇:(Eu, Mn) (GBAM type phosphor), and thelike.

One kind of these may be used singly, or two or more kinds may be usedin combination.

Red Phosphor

The phosphor of the present embodiment that includes a crystal phasehaving a composition represented by formula [1] or [2] above is used asthe red phosphor, but in addition to the phosphor of the presentembodiment, another orange through red phosphor can be used such as, forexample, a Mn activated fluoride phosphor, a garnet type phosphor, asulfide phosphor, a nanoparticle phosphor, a nitride phosphor, or anoxynitride phosphor. For example, the following phosphors can be used asthe other orange through red phosphor.

Examples of the Mn activated fluoride phosphor may include, for example,K₂(Si, Ti)F₆:Mn and K₂Si_(1-x)NaxAl_(x)F₆:Mn (0 < x < 1) (collectively,KSF phosphors), examples of the sulfide phosphor may include, forexample, (Sr, Ca)S:Eu (CAS phosphor) and La₂O₂S:Eu (LOS phosphor),examples of the garnet type phosphor may include, for example, (Y, Lu,Gd, Tb)₃Mg₂AlSi₂O₁₂:Ce, examples of the nanoparticle may include, forexample, CdSe, and examples of the nitride or oxynitride phosphor mayinclude, for example, (Sr, Ca)AlSiN₃:Eu (S/CASN phosphor),(CaAlSiN₃)_(1-x)′ (SiO₂N₂)_(x):Eu (CASON phosphor), (La, Ca)₃(Al,Si)₆N₁₁:Eu (LSN phosphor), (Ca, Sr, Ba)₂Si₅(N, O)₈Eu (258 phosphor),(Sr, Ca)Al_(1+x)Si_(4-x)O_(x)N₇-_(x):Eu (1147 phosphor), M_(x)(Si,Al)₁₂(O, N)₁₆:Eu (where M is Ca, Sr, or the like) (α-sialon phosphor),Li(Sr, Ba)Al₃N₄:Eu (where the x above is, in all instances, 0 < x < 1),and the like.

One kind of these may be used singly, or two or more kinds may be usedin combination.

Configuration of Light-Emitting Device

The light-emitting device according to the present embodiment includes afirst light emitter (excitation light source) and, as a second lightemitter, uses at least the phosphor of the present embodiment thatincludes a crystal phase having a composition represented by formula [1]or [2] above. The configuration of the light-emitting device is notlimited and can adopt a known device configuration as desired.

Examples of the device configuration and embodiments of thelight-emitting device may include those described in Japanese PatentLaid-open Publication No. 2007-291352, for example. In addition,examples of the form of the light-emitting device may includecannonball, cup, chip-on-board, remote phosphor, or the like.

Application of Light-Emitting Device

Applications of the light-emitting device are not particularly limited,and the device can be used in various fields where an ordinarylight-emitting device is used, but about the light-emitting device withhigh color rendering, among these, the device can be especially ideallyused as a light source of an illumination device or an image displaydevice.

In addition, the light-emitting device comprising a red phosphor havinga favorable emission wavelength can also be used in a red indicator lampfor a vehicle, or in an indicator lamp for a vehicle that is white andincludes the red.

Illumination Device

In one embodiment, the present invention can be configured as anillumination device comprising the light-emitting device as a lightsource.

In a case where the light-emitting device is applied to an illuminationdevice, the specific configuration of the illumination device is notlimited, and a light-emitting device such as those described above maybe appropriately incorporated into a known illumination device and used.Examples can include, for example, a plane emission illumination devicein which many light-emitting devices are lined up on a bottom surface ofa holding case.

Image Display Device

In one embodiment, the present invention can be configured as an imagedisplay device comprising the light-emitting device as a light source.

In a case where the light-emitting device is used as a light source ofan image display device, the specific configuration of the image displaydevice is not limited, but use with a color filter is preferred. Forexample, when configuring a color image display device using a colorliquid crystal display element as the image display device, an imagedisplay device can be formed by configuring the light-emitting device asa back light, and combining an optical shutter using a liquid crystalwith a color filter having red, green, and blue pixels.

Indicator Lamp for Vehicle

In one embodiment, the present invention can be configured as anindicator lamp for a vehicle comprising the light-emitting device.

A light-emitting device used in an indicator lamp for a vehicle, in aspecific embodiment, is preferably a light-emitting device radiatingwhite light. In the light-emitting device radiating white light, lightradiating from the light-emitting device preferably has a deviation duv(also known as “delta uv”,) from the blackbody radiation locus of alight color of -0.0200-0.0200 and a color temperature of 5,000 K or moreand 30,000 K or less.

A light-emitting device used in an indicator lamp for a vehicle, in aspecific embodiment, is preferably a light-emitting device radiating redlight. In this embodiment, for example, the light-emitting device mayabsorb blue light irradiating from a blue LED chip and emit red toconfigure a red light indicator lamp for a vehicle.

The indicator lamp for the vehicle includes illumination provided to avehicle with the objective of providing another vehicle, a person, orthe like with some sort of indicator, such as a headlight, side light,rear light, blinker, brake light, or fog light of a vehicle.

EXAMPLES

Hereafter, some specific embodiments of the present invention aredescribed as examples, but the present invention is not limited to thefollowing so long as the substance of the present invention is notexceeded.

Measurement Method Powder X-Ray Diffraction Measurement

Powder X-ray diffraction (XRD) was precision measured with the powderX-ray diffraction device SmartLab 3 (manufactured by Rigaku Co., Ltd.).

Measurement conditions are noted below.

-   Using CuKα bulb-   X-ray output:::: 45 kV, 200 mA-   Divergence slit = Automatic-   Detector = High-speed 1D X-ray detector (D/teX Ultra 250)-   Scan range 2θ = 5-95°-   Read width = 0.02°

Measuring Reflectance

A reflectance spectra was measured with an ultraviolet and visiblespectrophotometer (V-560, manufactured by JASCO Corporation) per thefollowing measurement conditions. The minimum reflectance in awavelength region from the emission peak wavelength to 800 nm was found,with a standard reflector made of foam resin-treated PTFE (Spectralonstandard reflector, manufactured by Labsphere, Inc.) treated as 100%.

-   Light source: Deuterium arc lamp (190-350 nm)-   : Tungsten iodine lamp (330-900 nm)-   Measured wavelength range: 200-800 nm-   Measurement interval: 0.5 nm

Measuring Emission Spectrum

The emission spectrum was measured with a fluorescence spectrophotometerF-4500 (manufactured by Hitachi High Technology Corporation) per thefollowing measurement conditions.

-   Light source: Xenon lamp-   Excitation wavelength: 455 nm-   Measured wavelength range: 200-800 nm-   Measurement interval: 0.2 nm

Measuring Quantum Efficiency

Quantum efficiency was measured with a quantum efficiency measurementsystem QE-2100 (manufactured by Ohtsuka Electronics Co., Ltd.) per thefollowing measurement conditions.

-   Light source: Xenon lamp-   Excitation wavelength: 455 nm-   Measured wavelength range: 200-850 nm-   Measurement interval: 0.5 nm

Evaluating Phosphor Characteristics

A red phosphor (examples 1-2) corresponding to the phosphor of thepresent embodiment that includes a crystal phase having a compositionrepresented by formula [1] or [2] above was prepared by manufacturing aphosphor according to the phosphor manufacturing method described aboveand measuring the emission spectrum and reflectance, after which aphosphor with a minimum reflectance in the wavelength region from theemission peak wavelength to 800 nm that satisfies the requirements ofthe present invention is selected. In addition, a phosphor ofcomparative example 1 in which the minimum reflectance in the wavelengthregion from the emission peak wavelength to 800 nm is 17.74% wasprepared as a comparison to the present invention.

The composition, minimum reflectance in the wavelength region from theemission peak wavelength to 800 nm, emission peak wavelength, full widthat half maximum, and relative emission intensity when the emissionintensity of the phosphor of comparative example 1 is treated as 1 ofeach phosphor are shown in Table 1. In addition, the XRD patterns andemission spectra of the phosphors in example 1 and comparative example 1are shown in FIGS. 1 and 2 , respectively.

The space group of the phosphors of examples 1 -2 was P-1 and theemission peak wavelength was near 644 nm. In addition, it can be seenthat the full width at half maximum is favorable, at 54 nm and 57 nmrespectively, and the emission intensity is greatly improved by severaltimes or ten times or more compared to the phosphor of comparativeexample 1, and when applied to a light-emitting device, a light-emittingdevice having favorable conversion efficiency can be obtained.

TABLE 1 Composition Ga/ (Al+Ga) Minimum reflectance from emission peakwavelength to 800 nm (%) Emission peak wavelength /nm Full width halfmaximum /nm Relative emission intensity iQE /% Comparative example 1SrLi(Al,Ga)₃N₄:Eu 0.17 17.74 646 55 1.0 2% Example 1 SrLi(Al,Ga)₃N₄:Eu0.17 37.95 642 54 4.2 No data Example 2 SrLi(Al,Ga)₃N₄:Eu 0.17 75.64 64457 14.4 59% Example 3 SrLiAl₃N₄:Eu 0.00 68.71 649 50 14.5 42% Example 4SrLiAl₃N₄:Eu 0.00 72.60 650 52 24.0 67% Example 5 SrLi(Al,Ga)₃N₄:Eu 0.1773.99 642 54 18.4 63% Example 6 SrLi(Al,Ga)₃N₄:Eu 0.20 70.61 640 55 16.761% Example 7 SrLi(Al,Ga)₃N₄:Eu 0.23 72.85 639 57 13.6 57% Example 8SrLi(Al,Ga)₃N₄:Eu 0.27 66.05 638 57 11.1 47% Example 9 SrLi(Al,Ga)₃N₄:Eu0.30 57.61 636 58 8.9 34% Example 10 SrLi(Al,Ga)₃N₄:Eu 0.33 78.97 634 5715.5 52% Example 11 SrLi(Al,Ga)₃N₄:Eu 0.40 74.39 633 55 15.0 60% Example12 SrLi(Al,Ga)₃N₄:Eu 0.50 72.32 629 58 9.3 47%

Next, phosphors in which the reflectance and the configuration of the MCelement in formula [1] (or MD element in formula [2]) were variouslymodified (examples 3-12) were prepared. The composition, minimumreflectance in the wavelength region from the emission peak wavelengthto 800 nm, emission peak wavelength, full width at half maximum,relative emission intensity when the emission intensity of comparativeexample 1 is treated as 1, and the internal quantum efficiency (iQE) ofeach example are shown in Table 1. Note that the space group was P-1 forall of examples 3-12. In addition, Table 2 shows the minimum reflectancein prescribed wavelength regions, and the difference or ratio betweenthe minimum reflectances associated with each region.

In addition, a commercially available CASN phosphor (BR-101/J,manufactured by Mitsubishi Chemical Corporation) having a compositionrepresented by CaAlSiN₃:Eu was prepared as reference example 1, showingan example of an existing phosphor. The space group of the phosphor ofreference example 1 was Cmc2₁, the emission peak wavelength was 646 nm,and the full width at half maximum was 87 nm.

TABLE 2 Reflectance A/% Reflectance B/% Reflectance C/% A - B A - C C/AEmission peak wavelength /nm Relative emission intensity Comparativeexample 1 17.74 19.57 18.90 -1.83 -1.16 1.07 646 1.0 Example 1 37.9537.84 35.43 0.11 2.53 0.93 642 4.2 Example 2 75.64 73.75 60.39 1.8915.25 0.80 644 14.4 Example 3 68.71 64.14 48.33 4.57 20.38 0.70 649 14.5Example 4 72.60 64.74 49.15 7.87 23.45 0.68 650 24.0 Example 5 73.9968.99 54.50 5.00 19.49 0.74 642 18.4 Example 6 70.61 67.12 54.23 3.5016.38 0.77 640 16.7 Example 7 72.85 69.27 56.32 3.58 16.54 0.77 639 13.6Example 8 66.05 65.24 55.00 0.81 11.05 0.83 638 11.1 Example 9 57.6157.41 50.18 0.20 7.44 0.87 636 8.9 Example 10 78.97 77.05 60.74 1.9318.24 0.77 634 15.5 Example 11 74.39 74.07 58.85 0.32 15.55 0.79 63315.0 Example 12 72.32 72.30 61.02 0.02 11.30 0.84 629 9.3 Reflectance A:Minimum reflectance from emission peak wavelength to 800 nm ReflectanceB: Minimum reflectance from emission peak wavelength to (emission peakwavelength - 50 nm) Reflectance C: Minimum reflectance from 400 nm to550 nm

XRD patterns of the phosphors in examples 4-10 are shown in FIG. 3 .Emission spectra of the phosphors in examples 4-9 and comparativeexample 1 are shown in FIG. 4A and emission spectra of the phosphors inexamples 10-12 and comparative example 1 are shown FIG. 4B. Normalizedemission spectra of the phosphors in examples 4, 5, and 9 and referenceexample 1 when emission peak intensity of the phosphors is defined as 1are shown in FIG. 5 . In addition, the reflectance spectra of thephosphors of each of the examples and the comparative example are shownin FIGS. 6A-D. The relationships of the relative emission intensities ofthe phosphors of each of the examples with [reflectance A - reflectanceB], [reflectance A --- reflectance C], [reflectance C/reflectance A] and[reflectance B/reflectance A], associated with the reflectances A, B andC, are shown in FIGS. 7A-D. Note that the emission peak wavelength ofthe phosphor of reference example 1 was 646 nm and the full width athalf maximum was 87 nm.

As shown in above examples, the phosphor of some embodiments can achievevarious emission peak wavelengths to match an application by adjustingthe composition. In addition, the phosphors of each example allexhibited extremely high emission intensity as compared to the phosphorof comparative example 1.

In addition, the full width at half maximum of the phosphors of eachexample was extremely narrow as compared to the phosphor of referenceexample 1, and by using such a phosphor, a light-emitting device havingboth favorable conversion efficiency and color rendering or colorreproducibility can be provided.

Next, results S1-S9 of simulations according to the characteristics of alight-emitting device comprising the phosphor of the present embodimentare described.

Assuming a SCASN phosphor having an emission peak wavelength of 620 nm(BR-102/D, manufactured by Mitsubishi Chemical Corporation) is used as afirst red phosphor, a phosphor of the examples and the comparativeexample shown in Table 3 below or a CASN phosphor having an emissionpeak wavelength of 646 nm (BR-101/J, manufactured by Mitsubishi ChemicalCorporation) is used as a second red phosphor, and a LuAG phosphor(BG-801/B4, manufactured by Mitsubishi Chemical Corporation) is used asa green phosphor, the emission spectra of white LEDs comprising each ofthe phosphors were calculated on the basis of information for theemission spectrum, the internal quantum efficiency (iQE), and the likeof each phosphor. All simulations were carried out assuming a blue LEDchip emitting light of 449 nm. In addition, once the color renderingindex Ra satisfies 90 or more, the amounts of the green phosphor and thefirst and second red phosphors were adjusted such that chromaticitycoordinates match the coordinates of 3000 K white light on the Planckcurve, and characteristics were compared. Results are shown in FIGS.8A-G. In addition, Table 3 shows the results of finding the colorrendering index Ra, the red color rendering index R9, and the conversionefficiency (LER) from each spectrum.

Note that “Phosphor Mass Relative Value” in Table 3 is a mass ratio ofeach phosphor when the total mass of each phosphor is treated as 100%.“Green” is the LuAG phosphor described above, “Red 1” is the first redphosphor described above, and “Red 2” is the second red phosphordescribed above.

TABLE 3 Green phosphor First red phosphor Second red phosphor Relativevalue of phosphor mass LER Lm/W_(opt) Ra R9 Green Red 1 Red 2 S1 LuAGSCASN Comparative example 1 72% 0% 28% 358 58 - S2 LuAG SCASN Referenceexample 1 80% 6% 14% 295 91 53 S3 LuAG SCASN Example 2 72% 8% 20% 311 9050 S4 LuAG SCASN Example 3 81% 7% 11% 297 90 57 S5 LuAG SCASN Example 482% 9% 9% 294 91 61 S6 LuAG SCASN Example 6 76% 9% 14% 311 91 50 S7 LuAGSCASN Example 7 69% 6% 24% 310 92 59 S8 LuAG SCASN Example 8 63% 4% 33%311 92 61 S9 LuAG SCASN Example 9 49% 0% 51% 312 90 63

As shown in Table 3, the light-emitting devices using the phosphors ofeach example had dramatically improved color reproducibility Ra ascompared to a case using the phosphor ofcomparative example 1, and inaddition, LER or R9 or both are improved compared to a case using thephosphor of reference example 1, and conversion efficiency and colorrendering or color reproducibility as well are superior. Note that inthe example using the phosphor of comparative example 1 for the secondred phosphor, the emission intensity of the red region was low andtherefore the value of R9 indicating the degree of color reproduction ofred was extremely low and could not be evaluated accurately.

As indicated above, according to some embodiments, a phosphor can beprovided having a favorable emission peak wavelength, narrow full widthat half maximum, and/or high emission intensity, and by including thephosphor, a light-emitting device, an illumination device, an imagedisplay device, and/or an indicator lamp for a vehicle having favorablecolor rendering, color reproducibility and/or favorable conversionefficiency can be provided.

Although various embodiments are explained with reference to thedrawings as described above, the present invention is not limited to theembodiments. It is clear that the person skilled in the art can conceivevarious examples of changes and modifications within the scope of claimsand it is understood that such examples of changes and modifications areof course included in a technical scope of the present invention.Additionally, each constituent in the above embodiment can bearbitrarily combined within the scope of the gist of the invention.

The present application is based on a Japanese Patent Application No.2022-007317 filed on Jan. 20, 2022 and a Japanese Patent Application No.2022-007319 filed on Jan. 20, 2022, the contents of which areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

Since the light-emitting device in the present invention is superior incolor rendering, color reproducibility and/or conversion efficiency, thelight-emitting device can be suitably used for an illumination device,an image display device, and an indicator lamp for a vehicle.

1-20. (canceled)
 21. An illumination device, comprising a light-emittingdevice as a light source, wherein the light-emitting device comprises afirst light emitter and a second light emitter that emits visible lightdue to irradiation with light from the first light emitter, and thesecond light emitter includes a phosphor that includes a crystal phasehaving a composition represented by formula [1] below,

wherein in formula [1] above, MA includes one or more elements selectedfrom the group consisting of Sr, Ca, Ba, Na, K, Y, Gd, and La, MBincludes one or more elements selected from the group consisting of Li,Mg, and Zn, MC includes one or more elements selected from the groupconsisting of Al, Si, Ga, In, and Sc, X includes one or more elementsselected from the group consisting of F, Cl, Br, and l. Re includes oneor more elements selected from the group consisting of Eu, Ce, Pr, Tb,and Dy, and a, b, c, d, e, and x satisfy the following expressions,respectively, 0.7 ≤ a ≤ 1.3 0.7 ≤ b ≤ 1.3 2.4 ≤ c ≤ 3.6 3.2 ≤ d ≤ 4.80.0 ≤ e ≤ 0.2 0.0 < x ≤ 0.2. wherein a minimum reflectance of thephosphor in a prescribed wavelength region is 20% or more, and theprescribed wavelength region is a region from the emission peakwavelength of the phosphor to 800 nm, and wherein the phosphor has ashort emission peak wavelength of from 620 to 648 nm in an emissionspectrum.
 22. The illumination device according to claim 21 wherein, informula [1], 80 mol% or more of MA is one or more elements selected fromthe group consisting of Sr, Ca. and Ba.
 23. The illumination deviceaccording to claim 21 wherein, in formula [1], 80 mol% or more of MB isLi.
 24. The illumination device according to claim 21 wherein, informula [1], 80 mol% or more of MC is at least one selected from thegroup consisting of Al and Ga.
 25. The illumination device according toclaim 21 wherein a space group of the crystal phase having thecomposition represented by formula [1] is P-1.
 26. The illuminationdevice according to claim 21 wherein a full width at half maximum (FWHM)in an emission spectrum of the phosphor is 70 nm or less.
 27. Theillumination device according to claim 21, further comprising a yellowphosphor and/or a green phosphor.
 28. The illumination device accordingto claim 27 wherein the yellow phosphor and/or green phosphor include atleast one phosphor selected from the group consisting of a garnet typephosphor, a silicate type phosphor, a nitride phosphor, and anoxynitride phosphor.